Field of the Invention
The present invention relates to an installation for the production of cold and/or heat.
Description of Related Art
Thermodynamic machines used for the production of cold, heat, or energy all relate to an ideal machine referred to as a Carnot machine. An ideal Carnot machine requires a heat source and a heat sink at two different temperature levels. It is therefore referred to as a dithermal machine. It is referred to as a driving Carnot machine when it operates no provide work and as a receiving Carnot machine (also known as a Carnot heat pump) when it operates by consuming work. In heat-engine mode, heat Qh is supplied to a working fluid GT from a hot source at the temperature Th, heat Qb is ceded by the working fluid GT to a cold sink at the temperature Tb, and net work W is delivered by the machine. Conversely, in heat-pump mode, heat Qb is taken up by the working fluid GT from the cold source at the temperature Tb, heat Qh is ceded by the working fluid to the heat sink at the temperature Th, and net work W is consumed by the machine.
According to the second law of thermodynamics, the efficiency of a dithermal (driving or receiving) machine, i.e. a real machine whether operating according to the Carnot cycle or not, is at most equal to that of the ideal Carnot machine and depends only on the source temperature and the sink temperature. However, practical implementation of the Carnot cycle, consisting of two isothermal steps (at the temperatures Th and Tb) and two reversible adiabatic steps, encounters several problems that have not been completely solved until now. During the Carnot cycle the working fluid may remain in the gaseous state at all times or it may undergo a liquid/vapor change of state during the isothermal transformations at the temperatures Th and Tb. When a liquid/vapor change of state occurs, heat is transferred between the machine and the environment with greater efficiency than if the working fluid remains in the gaseous state. With a change of state, and for the same thermal powers exchanged at the level of the heat source and the heat sink, the exchange areas are smaller (and therefore less costly). However, if there is a liquid/vapor change of state, the reversible adiabatic steps consist in compressing and expanding a two-phase liquid/vapor mixture. Prior art techniques are unable to compress or expand two-phase mixtures. In the present state of the art, it is not known how to carry out these transformations correctly.
To solve this problem, approximating the Carnot cycle has been envisaged by isentropically compressing a liquid and isentropically expanding a superheated vapor (driving cycle) and compressing the superheated vapor and isenthalpically expanding the liquid (receiving cycle). However, such modifications introduce irreversibilities into the cycle and greatly degrade its efficiency, i.e. the efficiency of the heat engine or the coefficient of performance or the coefficient of amplification of the heat pump.
So called “absorption”, “adsorption”, and “chemical reaction” methods have been developed for the production of cold at the temperature Tb and/or heat at an intermediate temperature Tm essentially using heat at a high temperature Th as an external energy source, plus a little work, in particular to circulate the heat-exchange fluids. If the function of the method is the production of cold, its efficiency is quantified by a coefficient of performance COP3, which is the ratio of the cold produced to the ‘costly’ energy consumed (heat at high temperature and work). When the function of the method is the production of heat at a useful temperature Tm, its efficiency is quantified by a coefficient of amplification COA3, which is the ratio of heat delivered at the temperature Tm to the ‘costly’ energy consumed (heat at high temperature and work).
The combination of a Carnot driving machine operating between temperatures ThM and TbM and a Carnot receiving machine operating between temperatures TbR and ThR could provide the same functions as said absorption, adsorption, or chemical reaction methods providing all the work supplied by the Carnot driving machine is recovered by the Carnot receiving machine. In the general case, the temperatures ThM, TbM, ThR, and TbR are different and the combination of the two Carnot machines is referred to as a “quadrithermal Carnot machine”. However, some temperatures may be the same (TbM=ThR=Tm or ThM=TbR=Tm), in which case the combination of the two Carnot machines is referred to as a “trithermal Carnot machine”.
The coefficient of performance or the coefficient of amplification of any trithermal or quadrithermal process is at best equal to the coefficients (CPPC3, COPC4, COAC3, or COAC4) of trithermal or quadrithermal Carnot machines operating between the same temperature levels, and is generally lower.
In the current state of the art, absorption, adsorption, or chemical reaction processes in practice have efficiencies much lower than those of corresponding trithermal or quadrithermal Carnot machines. The ratios COP3/COPC3 are typically of the order of 0.3.
Furthermore, many absorption, adsorption, or chemical reaction processes use water at low pressure (<10 kilopascals (kPa)) as the working fluid, which requires a perfect seal from the external environment and leads to solutions that are technically difficult to implement in order to integrate the various elements of the machine in the same low-pressure enclosure.